1. Technical Field
The present invention relates to a cryogenic refrigerator that uses a displacer.
2. Description of Related Art
Gifford-McMahon (GM) refrigerators are known as cryogenic refrigerators that use a displacer. The GM refrigerator causes a displacer to undergo a reciprocating motion within a cylinder, in order to vary a volume of an expansion space. Cooling is generated in the expansion space, by selectively connecting the expansion space to a return end and a suction end of the compressor in correspondence with this volume variation.
In a certain GM refrigerator, a drive shaft that drives the displacer is accommodated within a housing, and the pressure within a space (or assist space) formed at a tip end part of the drive shaft and the housing are adjusted.